1. Field of the Invention
The present invention relates to sequential punch presses, and particularly to a sequential punch press with a punch which can selectively punch a workpiece.
2. Description of Related Art
Various electronic devices are ubiquitous in modem society. For example, computer servers and routers pervade the business world. Enclosures of such electronic devices are usually formed by processes including punching.
Conventional means for forming enclosures from a workpiece comprise, for example, laser machining and conventional sequential punch machining. However, laser machining is costly and is therefore not widely used. Conventional sequential punch machining involves a series of stages of machining the workpiece. The workpiece is sequentially moved a same fixed distance at each stage of machining. This provides convenient machining when the workpiece is required to be machined at regular fixed intervals. However, it is problematic when the workpiece is required to be machined at irregular intervals. In such case, the conventional sequential punch press must be configured with suitable punches such that the punches simultaneously punch the workpiece in a single stroke. Thereupon, the entire workpiece is moved out from the punch press. Machining of the entire workpiece is completed within a single stage. The entire length of the workpiece must be moved out of the punch press in a single stage. Thus when the workpiece is very long, commonly 2 or 3 meters, the punch press must be equipped with a long lower plate to be able to perform the single-stage punching of the entire workpiece. All these requirements are inconvenient and time-consuming.